package com.rising.face.nio;

import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.util.Iterator;
import java.util.Set;

/**
 * @Author: rising
 * @Description:
 * @Date: create in 2021/1/23 16:48
 */
public class NIOServer {
    public static void main(String[] args) throws Exception {
        //创建ServerSocketChannel -> ServerSocket
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

        //得到一个Selector对象
        Selector selector = Selector.open();

        //绑定一个端口6666，在服务器监听
        serverSocketChannel.socket().bind(new InetSocketAddress(6666));
        //设置为非阻塞
        serverSocketChannel.configureBlocking(false);

        //把serverSocketChannel注册到 selector关心事件为OP_Accept；
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

        System.out.println("注册后的selectionkey 数量=" + selector.keys().size());

        //循环等待客户端连接
        while (true) {

            //这里我们等待1秒，如果没有事件发生，返回
            if (selector.select(1000) == 0) {//没有事件发生
                System.out.println("服务器等待了1秒，无连接");
                continue;
            }

            //如果返回的>0,就获取到相关的selectionKey集合
            //1、如果返回的>0，表示已经获取到关注的事件
            //2、selector.selectedKeys() 返回关注事件的集合
            //通过selectionKey 返回获取通道
            Set<SelectionKey> selectionKeys = selector.selectedKeys();

            //编列Set<SelectionKey>
            Iterator<SelectionKey> keyIterator = selectionKeys.iterator();

            while (keyIterator.hasNext()) {
                //获取到SelectionKey
                SelectionKey key = keyIterator.next();
                //根据key对应的通道发生的事件做相应的处理
                if (key.isAcceptable()) {//如果是OP_ACCEPT
                    //给该客户端生成一个SocketChannel
                    SocketChannel socketChannel = serverSocketChannel.accept();

                    System.out.println("客户端连接成功 生成了一个SocketChannel" + socketChannel.hashCode());
                    //将socketChannel设置为非阻塞
                    socketChannel.configureBlocking(false);
                    //将SocketChannel 注册到selector,关注事件为OP_READ，给socketChannel
                    //关联一个Buffer
                    socketChannel.register(selector, SelectionKey.OP_READ, ByteBuffer.allocate(1024));

                    System.out.println("客户端连接后，注册的selectionkey 数量=" + selector.keys().size());

                }

                if (key.isReadable()) {//发生OP_READ
                    //通过key反向获取对应channel
                    SocketChannel channel = (SocketChannel) key.channel();
                    //获取到该channel关联的buffer
                    ByteBuffer buffer = (ByteBuffer) key.attachment();
                    channel.read(buffer);
                    System.out.println("from 客户端 " + new String(buffer.array()));
                }

                //手动从集合中移除当前的selectionKey，防止重复操作

                keyIterator.remove();
            }

        }
    }
}
